1. Field of the Invention
The invention relates to a release agent spray device for a casting machine, as per the preamble of Claim 1.
2. Description of the Related Art
Release agent spray devices of said type are used for example as release agent spray systems for the automatic spraying of casting moulds in pressure-die-casting machines. With increasing demands on casting quality, service life, servicing, material consumption and environmental protection, the demands on release agent spray systems increase correspondingly.
It is known for the release agent to be discharged via one or more spray nozzles in intermittent spray bursts by virtue of a blockable release agent supply line which leads to the respective spray nozzle being opened only for a certain period of time during the spray burst, and compressed air simultaneously being supplied to the spray nozzle, such that release agent is sucked into the spray nozzle and is discharged from the latter, with compressed air assistance, as a spray jet. The laid-open specification DE 32 38 201 A1 and patent publication EP 1 468 745 B1 describe release agent spray devices of said type in which a control piston which can be actuated by means of control air is provided for opening and blocking the release agent supply line to the spray nozzle. In this way, the quantity of release agent discharged per spray burst is dependent inter alia on the adjustable stroke of the control piston and on the opening time of the latter, during which said control piston opens the release agent supply line. On account of the additional dependency on further parameters, such as release agent pressure, geometry and in particular cross section of the spray nozzle, and pressure and time duration of the spray air burst which is supplied to the spray nozzle and which sucks in the release agent, the release agent quantity which is sprayed per spray burst and spray nozzle is not precisely known and is also not precisely predefined in said conventional spray systems.
To obtain short cycle times in the casting process, for modern pressure-die-casting machines, there is a demand for correspondingly fast release agent spray systems, and accordingly very short spray times with a consistently good, reproducible spray characteristic. In particular, the spray characteristic and in particular the sprayed release agent quantity should also not be influenced by any switching delays of system components which are involved, such as check valves and the like. Furthermore, the sprayed release agent quantity should be kept to a minimum.
It is an object of the invention to provide a release agent spray device of the type specified in the introduction which permits a reliable discharge of a predefinable release agent quantity in a respective spray burst via one or more spray nozzles.